$ cat if-mail.pl 
#!/usr/bin/perl
exit 0 unless (my @lines = <STDIN>);
open(my $mail, "|-", join " ", "/usr/bin/mail", @ARGV) or die $!;
print $mail @lines;
$ LC_ALL=C ./if-mail.pl root@localhost -s "do not run echo; touch ~/zzz && ls ~/zzz - it does not make sense"
TEST
^D
ls: cannot access -: No such file or directory
ls: cannot access it: No such file or directory
ls: cannot access does: No such file or directory
ls: cannot access not: No such file or directory
ls: cannot access make: No such file or directory
ls: cannot access sense: No such file or directory
/home/aitap/zzz
$ ./if-mail.pl root@localhost -s "try running echo *"
TEST
^D

##</code><code>##

$ mail
       From: Krylov Ivan <aitap@tarkus>
         To: echo@tarkus, not@tarkus, root@localhost, run@tarkus
    Subject: do
 Message-ID: <E1VnDEf-0008HF-UG@Tarkus>
       Date: &#1055;&#1085;&#1076;, 02 &#1044;&#1077;&#1082; 2013 00:03:21 +0400
----------------------------------------------------------------

TEST
----------------------------------------------------------------
       From: Mail Delivery System <Mailer-Daemon@tarkus>
         To: aitap@tarkus
    Subject: Mail delivery failed: returning message to sender
 Message-ID: <E1VnDEg-0008HS-5L@Tarkus>
       Date: &#1055;&#1085;&#1076;, 02 &#1044;&#1077;&#1082; 2013 00:03:22 +0400
----------------------------------------------------------------

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  echo@tarkus
    Unrouteable address
  not@tarkus
    Unrouteable address
  run@tarkus
    Unrouteable address

------ This is a copy of the message, including all the headers. ------
<...>
       From: Krylov Ivan <aitap@tarkus>
         To: echo@tarkus, if-mail.pl@tarkus, root@localhost, running@tarkus
    Subject: try
 Message-ID: <E1VnDFD-0008Is-Co@Tarkus>
       Date: &#1055;&#1085;&#1076;, 02 &#1044;&#1077;&#1082; 2013 00:03:55 +0400
----------------------------------------------------------------

TEST
----------------------------------------------------------------
       From: Mail Delivery System <Mailer-Daemon@tarkus>
         To: aitap@tarkus
    Subject: Mail delivery failed: returning message to sender
 Message-ID: <E1VnDFD-0008Iy-K2@Tarkus>
       Date: &#1055;&#1085;&#1076;, 02 &#1044;&#1077;&#1082; 2013 00:03:55 +0400
----------------------------------------------------------------

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  echo@tarkus
    Unrouteable address
  if-mail.pl@tarkus
    Unrouteable address
  running@tarkus
    Unrouteable address

------ This is a copy of the message, including all the headers. ------
<...>